Crude (unrefined) animal and vegetable oils (referred to herein collectively as “natural oils”) are typically subjected to a variety of processing steps to remove specific undesirable components of the crude oil prior to sale. The type, number, and sequencing of processing steps can vary depending on the crude oil feedstock, refinery type (e.g. physical vs. alkaline) and configuration, target product markets, and the like. In general, crude natural oils are refined to remove excess quantities of “gums” (comprised primarily of phospholipids), free fatty acids, as well as various coloring components and volatile compounds.
Once removed from the crude oil, the refining byproducts are either sold directly into low-value markets such as animal feed, or further processed into higher-value products. Two major byproducts of the chemical refining processes of natural oils are soapstock and gums. In most natural oil refineries utilizing the chemical refining process, phosphoric acid or an equivalent acid is added to the crude oil to increase the solubility of the phospholipids (gums) in water. Next, a strong base, typically sodium hydroxide (NaOH) is added, reacting with the free fatty acids in the oil to form soaps (salts of free fatty acids). Water is then added to the oil to remove the soaps and solubilized gums. Soapstock is typically acidulated to generate free fatty acids. Gums are typically sold into low-value animal feed markets or upgraded to food-grade emulsifiers, e.g. lecithin.
In most chemical refining configurations, additional waste streams are generated which represent low- or negative-value byproducts. For example, it typically necessary to perform an additional water wash on the oil after the majority of the gums and soaps have been removed. The lipid content of this washwater (referred to as Soapstock Makeup) can contain from about 5% to about 20% soaps and other lipids, but the lipid content is generally not sufficiently high to justify the costs of further processing into value added products. In addition, all of the above referenced byproduct streams from the chemical refining process contain various amounts of saponifiable (triglyceride-comprising) material that are not converted to free fatty acids.